Parasequence Stacking Patterns, Third-Order Accommodation Events, and Sequence Stratigraphy of Middle to Upper Cambrian Platform Carbonates, Bonanza King Formation, Southern Great Basin

Ptychopariid trilobites from the Marjumiid biomere of Laurentia underwent a statistically significant morphological diversification that is concordant with proposed adaptive radiations of trilobites in each of the Cambrian biomeres. An analysis of a subset consisting of the biomere's most characteristic taxa, the Asaphiscacea, Raymondinacea, and Marjumiacea, also illustrates this morphological diversification. In detail, the total data set and subset show a limited range of morphologies near the base of the biomere and a large increase in range in the upper portion of the biomere.Regional assemblages from the Appalachians, Great Basin, and Texas were also studied to determine if they too show the larger-scale macroevolutionary patterns of trilobites from Laurentia as a whole. The regional assemblages illustrate similar, butnot identical, morphological diversifications, which are also similar to the overall Laurentian pattern. Subsets of the characteristic taxa also show this diversification. These results suggest that regional assemblages can be used to investigate these larger-scale macroevolutionary patterns.Causal mechanisms for the diversification patterns are not clear. Potential mechanisms include: (1) endemic evolution of new morphologies in Laurentia; (2) migration of new morphologies, including intra- and inter-continental migrations; and (3) environmental controls over the distribution of morphologies. Likely causes for the morphological diversification and its similarity among regions probably include aspects of all three mechanisms.

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High Resolution Sequence Stratigraphy of Silurian Strata in Tazhong Area

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.111 ◽

2013 ◽

Vol 734-737 ◽

pp. 111-116

Author(s):

Lei Zhang ◽

Lun Wei Zhu ◽

Xue Juan Zhang

Keyword(s):

High Resolution ◽

Sequence Stratigraphy ◽

Third Order ◽

Sequence Stratigraphic ◽

Stratigraphic Framework ◽

Tazhong Area ◽

Sequence Boundaries ◽

High Resolution Sequence Stratigraphy ◽

Comprehensive Study

According to the fundamental principles of high resolution sequence stratigraphy, this paper focused on the application of high resolution sequence stratigraphy to Silurian strata in Tazhong area. Based on the comprehensive study of logging, drilling and seismic information, the high resolution sequence boundaries of Silurian strata and two scales of datum level cycles (long-term and intermediate-term) can be recognized in Tazhong area. Seven chronstratigraphic boundaries can be recognized in Silurian strata, including four sequence boundaries, which were the transformation from datum level falling to datum level rising, and three flooding surfaces, which the transformation from datum level rising to datum level falling. The Silurian strata in Tazhong area can be divided into three third-order sequences which correspond to three long-term datum level cycles, and 11 fourth-order sequences (parasequence sets) relating to 11 intermediate-term datum level cycles. The classification aforementioned can much better solved the corresponding problem between the six lithological sections of Silurian strata and sequence formations, finally establishes the high resolution sequence stratigraphic framework of Silurian strata in Tazhong area.

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Non-trilobite arthropods from the Silver Peak Range, Nevada

Journal of Paleontology ◽

10.1017/s0022336000044449 ◽

2003 ◽

Vol 77 (4) ◽

pp. 706-720 ◽

Cited By ~ 7

Author(s):

Ben Waggoner

Keyword(s):

Great Basin ◽

Lower Cambrian ◽

Upper Cambrian ◽

Extant Taxon ◽

Lower Ordovician

Two non-trilobite arthropods are described from the Emigrant Formation (Lower Cambrian-Lower Ordovician) in the Silver Peak Range, Esmeralda County, Nevada. A Middle or Upper Cambrian “arachnomorph” arthropod with a phosphatic exoskeleton has been noted in previous faunal lists, but has not been previously described. This fossil is here named Quasimodaspis brentsae gen. et sp. nov. Q. brentsae belongs in the Aglaspidida, a close outgroup to the true chelicerates; this is the second report of an aglaspidid from the Great Basin. Esmeraldacaris richardsonae gen. et sp. nov. is a newly discovered arthropod from the lower Ordovician, from beds transitional between the Emigrant Formation and the overlying Palmetto Formation. It is a survivor of an early arthropod lineage that does not belong in any extant taxon, but which may also include the Ordovician Corcorania and the Cambrian Mollisonia.

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Trilobites from the upper part of the Deadwood Formation (Upper Franconian and Trempealeauan stages, Upper Cambrian), Black Hills, South Dakota

Journal of Paleontology ◽

10.1017/s0022336000038981 ◽

1997 ◽

Vol 71 (1) ◽

pp. 86-102 ◽

Cited By ~ 8

Author(s):

James H. Stitt ◽

Wendy Metcalf Straatmann

Keyword(s):

New Species ◽

South Dakota ◽

Sea Level ◽

Great Basin ◽

Black Hills ◽

Upper Cambrian ◽

Two New Species ◽

Study Interval ◽

Central Texas

Trilobites assigned to 29 genera and 39 species are reported from the Deadwood Formation in the Black Hills of South Dakota. Two new species, Prosaukia lochmani and Arcifimbria pahasapaensis, are described. Brachiopods are reported from the Taenicephalus Zone.A biostratigraphic zonation is established for the upper part of the Deadwood Formation. The Taenicephalus Zone in the lower part of the study interval is succeeded upsection by the Ellipsocephaloides Zone, both of which are assigned to the Franconian Stage. These two zones are overlain in turn by the Illaenurus and Saukia Zones of the Trempealeauan Stage. These zones are used to correlate this part of the Deadwood with coeval strata in Montana and Wyoming, central Texas, Oklahoma, and Alberta, Canada. The lowstand of sea level that occurred in the Great Basin at the time of the deposition of the Saukiella junia Subzone of the Saukia Zone probably extended eastward into the Black Hills, resulting in the absence of this fauna in the Black Hills.

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